Apparatus for producing fibrous structures



Dec. 1, 1970 w, s, ER ETAL 3,543,332

APPARATUS FOR PRODUCING FIBROUS STRUCTURES Filed June 28, 1968 UnitedStates Patent US. Cl. 188 4 Claims ABSTRACT OF THE DISCLOSURE Apparatusand method for producing filamentary material by extruding substantiallyaxially through an orifice comprising contacting the extruded filamentstream downstream of the orifice and prior to hardening with a pluralityof high velocity gas streams, each moving in a direction having a majorcomponent in the direction of extrusion of the filament stream in ashallow angle of tangential convergence therewith to attenuate thefilament stream.

This application is a continuation-in-part of US. application Ser. No.581,075; for William Sherwood Wagner and John Drew Roberts; filed Sept.21, 1966 and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to the production offilamentary materials. It is concerned particularly with novel apparatusfor spray spinning molten fiber-forming polymers.

Various proposals have been advanced heretofore in connection withintegrated systems for forming fibrous assemblies, such as non-wovenfabrics and the like, directly from molten fiber-forming materials. Ingeneral, the proposed systems envisioned an extrusion operation followedby collection of the extruded filamentary material in the form of acontinuous fabric, web or other desired fibrous assembly. When detailsare considered, however, the various proposals differed in substantialways.

The present invention also is concerned with the direct production offilamentary materials. A basic objective of the invention is to provideimproved methods and apparatus for spray spinning molten fiber-formingmaterials at high production rates and without forming shot orobjectionably short fibers which would detract from the desirability ofthe collected fibrous assembly.

In accordance with an embodiment of the invention, spinning nozzle meansare provided with an extrusion orifice for the fiber-forming materialand with a plurality of gas outlet passages spaced apart about theextrusion orifice to supply jets of high velocity gas for contacting theextruded filament stream prior to hardening of the filament. Thedirections of the gas jets are such that substantial drag forces areapplied to the extruded filament stream in the direction of extrusionfor attenuating or drawing the material leaving the extrusion orifice.Further, the gas passages are inclined so that their axes do notintersect the axis of the extrusion orifice. These directionalcharacteristics have been found to be particularly sig nificant inpreventing the formation of shot and preventing freeze-ups of theextrusion nozzle. They also serve to permit achievement of the desiredhigh rate of production of filamentary materials in which the filamentsare substantially continuous.

ice

While still in the zone of influence of the gas streams,

the filament is deposited on collector means that preferably movescontinuously. The gas flow swirls the filament sections about in arandom expanding conical pattern and they reach the collector whiletheir surfaces are somewhat tacky so that sufiicient self bonding occursto preserve to a substantial extent the relationships established at thetime of deposit on the collector. These relationships may includeinteresting three-dimensional effects contributing significantly toproduct bulk.

DESCRIPTION OF THE DRAWINGS A more complete understanding of these andother features of the invention will be gained from a consideration ofthe following detailed description of an embodiment illustrated in theaccompanying drawings in which:

FIG. 1 is a schematic view illustrating the major components of a systemfor producing filamentary materials in accordance with the invention;

FIG. 2 is a front elevational view of the nozzle and adapter of FIG. 1;

FIG. 3 is a cross sectional view of the nozzle and adapter along theline 33 in FIG. 2;

FIG. 4 is a side elevational view of the nozzle; and

FIG. 5 is a rear elevational view showing the threaded and of thenozzle.

The invention may be used in connection with the production of productsfrom any of the various materials that may be melted and extrudedthrough an orifice to form a filament. Examples of suitable types offiber-forming materials are preferably organic fiber-forming materialssuch as polyolefins, polyamides, polyesters, cellulose acetate,polyvinyl acetate, poly(methyl methacrylate), styrene copolymers, andthe like. Polyolefins such as polyethylene and polypropylene, andpolyamides such as ny lon 66, have sufliciently low melt temperaturesand sufficiently low melt viscosities, and they are thereforeparticularly convenient to use. Even materials which are normallydifficult to melt without decomposition, such as cellulose acetate, maybe used by adding a high boiling plasticizer as a melt depressant, ifnecessary. Inorganic fibers such as glass can also be spun using thepresent apparatus and process but are normally less preferable.

Referring to FIG. 1, the fiber-forming material is heated in an extruder2, and is extruded through nozzle means 4. Steam or other heated gas issupplied to the nozzle means 4 through a separate steam line 6, and thesteam is directed outwardly from the nozzle to surround the filament 8issuing from the nozzle. The filament 8 is projected by the gas to thesurface -of a rotating collecting drum 10. The filament 8 may not becompletely solidified when it reaches the drum and points ofintersection of the filament are joined together by self-bonding to forma mat 12. Of course, the distance between the drum 10 and the nozzlemeans 4 affects the extent of self-bonding in the mat. The mat 12 may beformed by entanglement of portions of the filament on the surface of thedrum without self-bonding, if desired. The product 12 may be used assuch, or it may be subjected to various treatments, such as calendering,needling, compressing, impregnation with latex or other filler, orembossing to form various structures.

The nozzle 4 is supported on an adapter 14 which is secured over theoutlet of the extruder 2 by screws 16. The adapter 14 has a centralopening 18 through which the molten fiber-forming material is conductedto the nozzle. The passage 18 is internally threaded at the end oppositethe extruder to receive a threaded shank 20 on the nozzle 4. The screwthreads on the shank portion 20 and 3 in the passageway 18 cooperate toclamp the base 22 of the nozzle tightly against the face of the adapter14.

The nozzle has a central passage 24 which terminates in an extrusionorifice 26 through which the fiber-forming material is extruded. Thenozzle 4 also has a plurality of gas outlet passages 28 which are spacedaround the central passage 24. Each of the gas passages 28 is inclinedand is as long as is necessary for directing the gas in the desiredpath. All of the passages 28 preferably are inclined in the samedirection with respect to the orifice central axis and they arepreferably equally spaced, so that the gas stream issuing from each ofthe passages 28 has substantially the same effect on the filament streamissuing from the orifice 26.

Gas under pressure is supplied to the passages 28 from the adapter 14.The adapter has a passage 30 which is internally threaded to receive aconventional coupling 32. The passage 30 communicates with an annularheader 34. The base 22 of the nozzle 4 has an annular groove 36 whichinterconnects the ends of the gas passages 28 and which is substantiallyaligned with the header 34 for distributing gas from the header to thepassages 28. The groove 36 communicates with the header 34 regardless ofthe angular position of the nozzle 4 relative to the adapter 14. Thus,when the base 22 of the nozzle is screwed tightly against the adapter14, it is not necessary to turn the nozzle 4 to a predetermined angularposition in order to establish communication between the source of gasand the passages 28.

In operation, fiber-forming material is heated to a molten state in theextruder 2 and passes through the opening 18 in the adapter and throughthe passage 24, from which the molten material is extruded through thenozzle 4. At the same time, gas under pressure is conducted through thecoupling 32 into the header 34, and

from the nozzle groove 36 to the gas passages 28. The gas is preferablyheated above the melting temperature of the material being extruded andis compressed to cause substantial expansion of the gas as it passes outof the passages 28. The gas pressure should be high enough to assurethat the gas jets issuing from the passages 28 attain velocitiessuificiently greater than the extrusion velocity of the filament toenable the gas to exert an attenuating drag on the filament in an axialdirection. The gas also swirls the filament 8 about in a randomexpanding conical pattern in a downstream zone of turbulence, assuggested diagrammatically in FIG. 1. Collection of the filamentarymaterial preferably occurs continuously as the surface of the drum 10moves through the path of the material projected from the nozzle means4.

The construction of the nozzle means may take various forms. However, inall cases particularly careful attention should be given to therelationships established between the gas passages and the extrusionorifice. A brief discussion of some of the factors involved will serveas a basis for establishing particular configurations.

It is important that gas flow patterns be established which will notexpose the outlet of the extrusion orifice to unnecessary cooling orchilling effects. If the temperature of the fiber-forming material inand just beyond the extrusion orifice is not kept high enough, nozzlefreezeups and/or the formation of shot will occur. Moreover, We havefound that these difficulties cannot be avoided by simply increasing thetemperature at which the gas is supplied to the nozzle means. One reasonis the practical one that much of the potential energy of the gas willbe transformed into kinetic energy in the process of imparting to thegas the high velocity required for attenuating the coarse filamentstream issuing from the extrusion orifice. That is to say, the expansionof the gas as it moved through the air passages and into a zone ofatmospheric or ambient pressure will necessarily be accompanied by amarked drop in temperature in any truly practical system. Another reasonis that too high a gas temperature in the zone where the moving gas isapplying attenuating forces to the filament would reduce the tensilestrength of the filament in that zone to such an extent that it would bebroken up into undesirably short lengths.

Correlation of these factors is achieved in accordance with theinvention by effectively isolating the extrusion orifice from thechilling effects of the gas flow while bringing the gas flow to bearupon the filament stream at a downstream zone. For effective isolationit is important not only that the gas be directed along paths displacedfrom the extrusion orifice but also that the primary gas paths be suchas to avoid the creation of secondary flow patterns capable of producingundesired chilling at the extrusion orifice outlet. It has been found,for example, that gas streams directed along paths the axes of whichintersect at the filament stream will create a zone or lobe of turbulentair flow extending back along the filament axis in the upstreamdirection, and that this secondary flow effect can cause nozzlefreeze-ups. Such difficulties have been overcome however through the useof gas passages which are inclined in a distinctive manner.

The nature of the inclination of the several passages 28 shown in thedrawings can best be explained by reference to the positions of thepoints A and B indicated in FIGS. 2 and 5. Point A represents the pointof intersection of the central axis of a passage 28 with a planeperpendicular to the axis of the extrusion orifice at the outlet of thepassage 28 (e.g., the plane of the face 29 of the nozzle means shown inFIG. 3). Point B represents the point of intersection of the centralaxis of the passage 28 with another plane perpendicular to the axis ofthe extrusion orifice at the inlet of the passage 28 (e.g., the plane ofthe base of the groove 36 in FIG. 3). The inclination of the passageaxis is such that the points A and B are displaced angularly withrespect to each other about the axis of the extrusion orifice, and thepoint A is radially closer to the axis of the extrusion orifice than isthe point B.

The disposition of the point A closer to the extrusion axis than point Bgives the gas passage 28 an inclination component tending to causeconvergence of its axis with the extrusion axis at a point in front ofand displaced from the nozzle means 4. However, the skew efiect stemmingfrom the angular displacement of the points A and B with respect to eachother prevents actual intersection of the air passage axis with theextrusion axis. The degree of skew should preferably be great enough toassure that the cylindrical projection of the passage outlet openingalong the extended axis of the passage will not substantially overlap orintersect with the cylindrical projection of the extrusion orifice alongthe extrusion axis.

When the gas passages are skewed in this fashion, it becomes possiblefor the high velocity gas streams issuing therefrom to apply the desiredattenuating forces to the filament downstream of the extrusion orificewithout creating those secondary flow effects, such as turbulenue lobesextending back to the orifice outlet, which would result in nozzlefreeze-ups and/ or the production of shot.

SUMMARY OF THE INVENTION More specifically, the spray-spinning nozzlewhich is best suited for use with organic thermoplastic fiber-formingpolymers is designed to attenuate the fibers while still in the plasticstate, without excessive fiber breakage. Thus, the fiber is retainedsubstantially as a continuous fiber or long-staple fiber. This isaccomplished by attenuating the molten fiber exiting from the extrusionorifice with the jets of gas at a relatively shallow angle ofconvergence wherein the gas jet tangentially contacts the extrudedfiber. The angle of convergence is measured in a first plane containingthe orifice axis and a projection of the passage axis. The first planeis defined by the axis of the extrusion orifice 26 and by a lineextending perpendicularly to the extrusion orifice axis and passingthrough the center of the outlet opening A of one of the gas passages.The projection of the gas passage axis on the first plane intersects theorifice axis, the acute angle of intersection of the projected passageaxis and the orifice axis of the nozzle is the convergence angle. Thisangle is a shallow angle converging toward the fiber axis. Theconvergence angle preferably ranges from about 3 to degrees and morepreferably from about 4 to 7 degrees. However, as noted above, becausethe axis of the fiber extrusion and the axes of the gas streams areskewed with respect to each other, the respective axes do not actuallyintersect.

The skew angle is measured in a second plane that includes the orificeaxis and is perpendicular to the first plane. The projection of the axisof the gas passage 28 on the second plane intersects the orifice axis.The acute angle of intersection of these lines in the second plane isthe skew angle. This angle is between about 1 and 10 degrees, andpreferably between 1 and 7 degrees. Therefore, the fiber attenuation iseffected by the close proximity of the gas axis to the fiber axis asthey pass each other at their closest point. This closest point iscalled the convergent point.

The distance between the aforementioned axes at the convergent point isreferred to as the convergent diameter. The convergent diameter rangesfrom about 0.5 to 18 millimeters and preferably from about 1 to 10millimeters. The convergent point occurs at a distance of from about 12to 126 millimeters from the fiber extrusion orifice. This distance canbe varied in accordance with the convergence angle and the skew angle.It will be readily recognized by those skilled in the art that thevarious measurements noted above are interrelated and therefore thesetting of certain angles and distances predetermines certain of theother angles and distances.

Various gas or jet pressures can be utilized in the present invention.For the gas jet dimensions described herein, pressures between about 10and 100 pounds per square inch gauge are normally used. However, higheror lower pressures can be used, depending upon the particular desiredoperating conditions, the gas jet openings, the fiber being extruded andthe like. Pressures of from about 20 to pounds per square inch gaugehave been found to be particularly desirable for organic fibers usingthe gas jet more specifically described herein.

Of course, in achieving optimum conditions for particular commercialoperations due regard must be had for the specific material andprocessing conditions. The inclinations selected for thenon-intersecting axes of the generally converging gas jets may dependfor example upon such factors as gas temperature, the velocity attainedby the gas, the temperature and melt viscosity of the fiber-formingmaterial, and the deposition pattern at the zone of collection.

The following example will serve to further illustrate the principles ofthe invention.

EXAMPLE I In this instance the apparatus shown in the drawings wasemployed to produce a narrow non-woven fabric made up of substantiallycontinuous filaments.

The nozzle passages had the following dimensions: diameter of extrusionorifice 26, 0.030 inch; diameter of each gas passage 2-8, 0.082 inch;radial distance between the extrusion axis and the axis of each passage28 at the point where it intersects the groove 36, 0.290 inch; radialdistance between the extrusion axis and the axis of each passage 28 atthe outlet end of the passage, 0.197 inch; circumferential displacementof the axis of each passage 28 between the passage inlet and the passageoutlet (measured as the perpendicular distance between parallel planes,one of which contains the axis of the extrusion orifice 26 and the pointof intersection of the passage axis with the base of the groove 36 andthe other of which intersects the passage axis at the outlet end of thepassage), 0.084 inch; the distance along the extrusion axis between theoutlet of the extrusion orifice and the plane containing the outlets ofthe gas passages 2-8, 0.281

inch; and the perpendicular distance between the plane containing theoutlets of the gas passages 28 and the plane containing the inlets ofthe gas passages 28, 0.420 inch.

The angular relationships of the gas passages 28 with respect to theaxis of the extrusion orifice 26 were measured graphically. The angle ofconvergence was 12 degrees and the skew angle was 2 degrees.

Nylon 66 (polymeric condensation product of adipic acid andhexamethylene diamine) was supplied to the extruder. The extruder andadapter were heated to 310 C. and the polymer was melted in theextruder. The speed of the extruder screw was regulated to provide aflow rate of molten polymer of 2 lbs. per hour through the nozzleorifice.

A steam line was connected to the coupling 34 in the adapter 14 andsteam was supplied continuously to the nozzle at 350 C. and 40 p.s.i.g.

The collector was in the form of a drum having a smooth metal surfacespaced from the extrusion orifice a distance of about 2 ft. It wasrotated continuously at a surface speed of 3 ft. per minute to produce a4 inch wide band.

With the system in operation, the steam jets from the passages 28attenuated the melt stream of polymer into a continuous filament rangingfrom approximately 1 to 5 d.p.f. without producing shot. No tendencytoward nozzle freeze-up was observed. The filamentary material collectedon the drum exhibited a skin effect on the side thereof facing the drumand a loft or bulk effect on the opposite side. The non-woven fabricweighed approximately 5 oz. per square yard. The non-woven fabric hadsuflicient tensile strength to withstand substantial pulling forces.

It will be understood, of course, that these specific conditions andconfigurations described in detail herein are exemplary only, and thatthe invention is susceptible of embodiment in a variety of forms whichwill be evident to persons skilled in the art from the foregoing.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Apparatus for producing organic thermoplastic filamentary materialcomprising nozzle means having an extrusion orifice for fiber-formingmaterial and a plurality of gas outlet passages spaced from saidextrusion orifice and having non-intersecting axes spaced apart aboutthe axis of said extrusion orifice, the axis of each of said gas outletpassages being so inclined that such axis is closer to the axis of theextrusion orifice at the outlet end of the passage than at an interiorzone of the passage so as to direct the gas stream in a convergenceangle with the axis of the extrusion orifice of from about 3 to 15degrees and so that the location of the passage axis at the outlet endof the passage is displaced about the axis of the extrusion orifice withrespect to the location of the passage axis at an interior zone of thepassage so as to form a skew angle of from about l to 10 degrees withrespect to the axis of the extrusion orifice, means for extruding moltenfiber-forming material through said extrusion orifice, and means forsupplying said passages with gas under pressure to be projected fromsaid passages to contact and attenuate the stream of fiber-formingmaterial issuing from said extrusion orifice.

2. The apparatus according to claim 1 wherein said nozzle means isprovided with at least three of said ,gas passages and wherein theoutlet ends of all of said gas passages are displaced from their inletends about the axis of the extrusion orifice in the same circumferentialdirection.

3. The apparatus according to claim 1 wherein the inclination of theaxis of each of said gas passages is such that the projection of theoutlet opening along the passage axis approaches without intersectingthe projection of the extrusion orifice along its axis.

8 4. The apparatus according to claim 1 wherein the 3,266,969 8/ 1966'Makansi. gas outlet passages are positioned behind the eXtruSi0n3,282,668 11/1966 Mabru 6512 orifice. 3, 17,6 4 1/1962 Ladisch 18-25References Cited 3,309,734 3/1967 Bynum et a1 264176 3,436,792 4/ 1969Hench. FOREIGN PATENTS i 296,015 5/1965 Netherlands. 3 634 623 1962Canada. 3,423,266 1/1969 Davles et a1. 1 450274 7/1966 Franc 3,441,4684/1969 Siggel 64 a1. 10 2,121,802 6/1938 Kleist et a1. 49-1 I I2,331,945 10/1943 Pazsiczky et a1. JULIUS FROME Primary Exammer 2,37,540- 4/1945 n 18-25 I. H. WOO, Assistant Examiner 2,411,660 11/1946Manning. 2,437,263 3/1943 Manning. 15 2,508,462 5/1950 Marshall 18-8 182 5; 264 12, 210'

